Non-invasive patient interface devices are used in a variety of medical procedures, such as emergency ventilation, anesthesia delivery and recovery, aerosolized medication delivery, augmentation of natural breathing, supplemental oxygen delivery, mechanical ventilation, weaning from mechanical ventilation and for treating Obstructive Sleep Apnea. In the later case continuous positive airway pressure (CPAP) or continuous variable-level positive airway pressure (VPAP) is delivered through the interface device into the patient's airway during sleep to prevent airway obstruction. OSA is unique to all positive airway pressure (PAP) applications in that the patient is otherwise healthy and the therapy has to be a minimally obtrusive in order to not disrupt the patient while sleeping, whereas in other PAP applications disrupting sleep is of negligible concern. There are three different forms of NIV interface devices; Nasal Interfaces, Oral Interfaces and combined Oral-Nasal Interfaces. Of the Nasal Interface type, there are two categories: Nasal Masks and Nasal Interfaces or Cannulae.
Nasal ventilation interface devices are typically used for supplying supplemental oxygen gas to a person's lung during their natural breathing by placing the tips of the device within the person's nostrils or nares. These devices are constructed of tubing diameters substantially smaller than the diameter of the nostrils since the volumetric demand for the supplemental oxygen is very low (<2 LPM) negating the need for large bore tubes, and since the user must be able to breathe room air around the outside of the interface tubes prongs which are placed in the nostrils.
Oxygen nasal cannulae typically comprise a main base tube positioned horizontally under the nose from which two prongs extend at right angles upward and into the nostrils. With some devices, these prongs are designed to pinch the nostril septum to facilitate retention and sometimes are tilted toward each other at their tips to facilitate pinching.
Typically, if not always, the base tube has a through lumen and the oxygen supply tubing usually attaches to and extends from both sides of this base tube, typically routed around the ears then to the front of the neck to secure the apparatus to the patient. In addition to these oxygen interface tubes, a medical practice has been established to use larger nasal interface tubes that seal the nostrils in order to provide positive airway pressure (PAP) ventilation therapy. The practice is especially common in neonates because of the trauma associated with invasive tracheal intubation.
There are two basic forms of nasal interface tubes; non-sealing nasal interface tubes for supplemental oxygen therapy and sealing nasal interface tubes for PAP ventilation.
Recently special versions of sealing nasal interface tubes have been developed which are intended to improve PAP ventilation; however as shall be explained, these designs have significant deficiencies especially when used in OSA applications.
Agdanowski, U.S. Pat. No. 4,648,398 describes an expandable foam-tipped nasal prong wherein the user compresses the foam for insertion into the nostril then the foam re-expands to contact the nostril wall. The nasal prongs are right angle extensions from a base tube like oxygen therapy interface tubes. The Agdanowski device has two significant deficiencies especially when used in an OSA application: (1) The traditional base tube—right angle prong configuration is inherently resistant to flow because air which is forced into the base tube from both sides collides in the middle of the base tube and the air must make an abrupt directional change into the prongs. Generally, a resistant, turbulent design in an OSA application is undesirable because it causes extra noise (which is irritable to the user and bed partner) and because the user must compensate by increasing the pressure setting (which is less comfortable to the user). Increasing the pressure setting is more demanding on the seals, requiring the device to fit tighter to the user's nose (also less comfortable to the user). In non-OSA applications a resistive, turbulent design is acceptable since noise or higher pressure is of no concern to the user. (2) The Agdanowski device also does not allow the nasal prong portion to align correctly with the user's nostril canal.
However, alignment is key in OSA applications because unaligned prongs are uncomfortable. For example, Winthrop, U.S. Pat. No. 5,682,881 describes an interface tubes with an adhesive-backed foam strip placed on the skin below the nose for securing the interface tubes system in place. While adhesive backed securement systems are common is various short-term therapy applications, their viability in long term or repeated use is questionable. The Winthrop device also has the airflow resistance and alignment problems previously noted.
Trimble, U.S. Pat. No. 4,782,832 describes a nasal interface with a hard manifold positioned under the nose from which two frustoconical corrugated members extend for insertion into and sealing against the nostrils. The manifold is suspended below the nose by a bracket extending down from the forehead between the eyes and down the bridge of the nose. A gas supply tube is attached to the bracket. This bracket and manifold arrangement is an improvement for users who want the tubing away from their mouth or ears, however this configuration is obtrusive and not conducive to vision especially if wearing glasses. Additionally, discomfort from the hard plastic brackets and manifolds are common. Similar designs are described in Bordewick, et al., U.S. Pat. No. 6,418,928, and Bordewick U.S. Pat. No. 6,431,172. This family of devices is known commercially as the ADAM (airway delivery and management) Circuit or Nasal Pillows.
Wood, U.S. Pat. No. 6,478,026 describes a PAP nasal interface tubes comprised of a conventional oxygen interface tubes tubing configuration (a horizontal base tube positioned under the nose from which two prongs extend upward at right angles for insertion into the nostrils). The prongs comprise oval cross sections and a concentric ring at their tips. Similar designs are described in Wood, U.S. Pat. No. 6,595,215, Wood, U.S. patent application Ser. No. 2002/0092527, Strickland U.S. Pat. No. 6,679,265, and Wood, U.S. patent application Ser. No. 2003/0116163.
Interface tubes prongs with oval cross sections have been in commercial use since at least 1987, for example in Trimble, U.S. Pat. No. 4,782,832, however, an oval cross section has no practical value for PAP usage. The prong material must be significantly more compliant than the nostril tissue for the requisite comfort, and hence the nostril structure will shape the prong to conform to the nostril regardless of the shape of the prong. Indeed, in pediatric and adult applications, a prong with a circular cross section is as comfortable and seals as well as does an oval cross section prong, assuming they are both fabricated using the correct material softness.
Additionally, some of the devices have the problems of requiring deep interface cannulation of the prongs into the nose for sealing and retention; deep interface cannulation is highly undesirable to many users and may cause mucosal irritation or errosion. Finally, this family of inventions still possesses the nostril-prong alignment problems, flow turbulence problems, obtrusiveness, ear and cheek discomfort, and discomfort while user is lying on their side.
MacRae, U.S. Pat. No. 6,644,305 describes a medicine inhaler that has a waist-shaped tip that seals with the nostril. De Voss, U.S. patent application Ser. No. 2002/0046756 describes an oxygen nasal interface tubes with left and right nostril prongs that pinch the nasal septum in order to retain the device in place. Pinching is accomplished by tilting the distal tips toward each other and the tilt and spacing can be adjusted in order to produce enough pinching force to achieve retention. This design is unacceptable in many PAP applications, because a pinch force of greater than about 2 lbs. compression is required for adequate pinching in adults, which cannot be tolerated for extended durations. A slight amount of repeated or long term pinching can be tolerated (<1 lbs.), however this is insufficient for retaining an interface tubes in place.
Light nostril septum pinching by PAP nasal interface tubes has been previously successfully employed in the art described in Trimble U.S. Pat. No. 4,782,832 and Wood U.S. Pat. No. 6,478,026, however in these cases other primary retention features are used to secure the apparatus in place and septum pinching is a secondary retention feature and likely less than 1 lbs. compression.
Curti, U.S. Pat. No. 6,439,234 describes a non-sealing oxygen nasal interface tubes with exhalation CO2 sampling. The base tube between the nasal prongs is divided to create two separate tubing paths, one for oxygen delivery (inhalation) and one for CO2 sampling (exhalation). This device has utility in anesthesia situations where CO2 monitoring is necessary and its teachings and embodiments are considerably different than that which is required for PAP applications.
In summary there are five significant requirements of a PAP nasal interface tubes interface that are not adequately addressed in patient interface devices especially for OSA applications: (1) low resistance flow dynamics; (2) a comfortable and effective nostril seal without requiring deep penetration into the nose; (3) a simultaneously comfortable, unobtrusive and non-irritating system to retain the device to the nose, face and head; (4) a system or device that is easy to attach and remove; and (5) the overall apparatus must be minimally obtrusive, comfortable and ergonomic, allowing a user to speak, see, wear glasses, drink, and talk on the phone while being worn before falling asleep, and allowing the user to comfortably lay on their side during sleep without shifting the device or dislodging the portion that seals to the nose. Most of the prior art is useful and applicable only for PAP applications in which the patient is unconscious or heavily sedated thus unaware of the noted deficiencies.
As will be described in the subsequent sections, the present invention(s) disclosed herein solves the various deficiencies that exist with the currently available PAP nasal interface tubes devices, especially with respect to the requirements of an OSA user.